1. Field of the Invention
The present invention relates to a method and apparatus for gushing an air stream into a metal mold in an injection molding machine for the purpose of molding of a hot-molten substance, especially a synthetic resin.
2. Description of the Prior Art
The components and structure of synthetic resin injection molding machines have been developed for the purpose of high speed molding because of a demand for high speed molding in addition to precise molding.
Although various machine manufactures have simultaneously made an effort toward the research and development of injection molding machines for the purpose of the structural improvement from the standpoints of several functions such as resin-melting ability, resin injectability into a cavity and metal molding-cooling ability, satisfactory high speed molding have not been achieved till now because of restriction on the above respects.
When the gate is opened in the case of runnerless injection molding, for example, there may sometimes offer inconvenience of leakage of the molten resin such a drip of the molten resin as a "pendulous efflux" and a "string pulling" phenomenon. However, satisfactory high-speed molding is very difficult for all resins, even if cooling solidification of the resin or the gate portion, namely maintenance of the gate in a clogged state compulsatorily inhibits leakage of the molten resin to perform rapid opening and closing operations of the metal molding in order to prevent the above phenomena.
Because high-viscose styrol resins can achieve complete high-speed molding inspite of a material, which relatively less likely produce a pendulous efflux of the resin and the strain pulling phenomenon on the gate, the opening and closing speeds are delicately adjusted for each time according to the viscosity and the molding temperature of the resin and the size and shape of the molding.
Conventional injection molding machines have raised a problem in that efficient and effective molding can be made because of a pendulous efflux and a string pulling of the molten and semi-molten resin on the gate portion regardless of the intention of improvement in the mechanical properties in the case of high speed molding.